Laurence, Lionel · London, School of Optics · leaf 92
lens is a transparent body usually made of glass,bounded by two surfaces, both of which are curved or the one may be plane.It is usually surrounded by air. This definition covers all forms of convexand concave sphericals, as well as cylindrical and other special forms of lenses. Prismatic… … Fig. 85. the base of the prism B C D, so that those refracted by the one prism meetthose refracted by the other. One ray, viz., G C D H suffers no deviationsince it coincides with the base of both prisms; L and M are incident nor-mally to both surfaces, and are therefore also not deviated. If the…
Optics
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